Proteomic analysis of differentially expressed proteins in normal human thyroid cells transfected with PPFP

Simultaneous Inhibition of EGFR and HER2 via Afatinib Augments the Radiosensitivity of Nasopharyngeal Carcinoma Cells

Ionizing radiation (IR) is the central component of the therapeutic scheme for nasopharyngeal carcinoma (NPC) at present. Previous studies show that inhibition of epidermal growth factor receptor (EGFR) enhances the radiosensitivity of NPC; however the effects of EGFR-targeted agents are limited. In this study, we observed that simultaneously inhibition of EGFR and HER2 by afatinib could augment the radiosensitivity of NPC cells; this approach has an advantage over erlotinib-mediated inhibition of EGFR alone. The afatinib-induced augmentation of NPC cell radiosensitivity was associated with increases in apoptosis and accumulation of DNA damage that were induced by radiation. In addition, the crosstalk between radiation-induced activities and EGFR-, and HER2-related downstream pathways may contribute to the enhancement of radiosensitivity. Our findings indicate the potential of repositioning afatinib or other ERBB-family-targeted agents for improving radiation response in NPC cells.

Exosomes increased angiogenesis in papillary thyroid cancer microenvironment

Tumour-derived exosomes under hypoxic conditions contain informative miRNAs involved in the interaction of cancer and para-carcinoma cells, thus contributing to tissue remodelling of the tumour microenvironment (TME). Exosomes isolated from hypoxic papillary thyroid cancer cells, BCPAP cells and KTC-1 cells enhanced the angiogenesis of human umbilical vein endothelial cells (HUVECs) compared with exosomes isolated from normal thyroid follicular cell line (Nthy-ori-3-1), normoxic BCPAP or KTC-1 cells both in vitro and in vivo. miR-21-5p was significantly upregulated in exosomes from papillary thyroid cancer BCPAP cells under hypoxic conditions, while the exosomes isolated from hypoxic BCPAP cells with knockdown of miR-21-5p attenuated the promoting effect of angiogenesis. In addition, our experiment revealed that miR-21-5p directly targeted and suppressed TGFBI and COL4A1, thereby increasing endothelial tube formation. Furthermore, elevated levels of exosomal miR-21-5p are found in the sera of papillary thyroid cancer patients, which promote the angiogenesis of HUVECs. Taken together, our study reveals the cell interaction between hypoxic papillary thyroid cancer cells and endothelial cells, elucidating a new mechanism by which hypoxic papillary thyroid cancer cells increase angiogenesis via exosomal miR-21-5p/TGFBI and miR-21-5p/COL4A1 regulatory pathway.

Telomerase reverse transcriptase induced thyroid carcinoma cell proliferation through PTEN/AKT signaling pathway

Thyroid carcinoma is the most common endocrine malignant tumor in the world, and so, there is a requirement to develop novel molecular targets for thyroid cancer diagnosis and treatment. Telomerase reverse transcriptase (TERT) was revealed to promote cell proliferation in a number of types of cell. To evaluate whether and how TERT functioned on papillary thyroid cancer (PTC) cell proliferation, the present study constructed TERT over‑expression [recombined (r)TERT plasmid group] and interference [small interfering RNA (si)‑TERT group] models by liposome transfection respectively to study the molecular mechanisms. The transfection efficiency was first detected by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting to analyze TERT levels compared with the negative control (NC) and control groups. Then MTT and carboxyfluorescein diacetate succinimidyl ester assays were performed to determine living cell proliferation and total cell proliferation respectively. Propidium iodide assay was used to detect alterations in cell cycle progression. RT‑qPCR and western blotting were performed to detect associated factor variation. The results demonstrated that, following the generation of TERT overexpression or silencing PTC cells, the living cells and also total cell proliferation increased significantly in the rTERT group, and decreased significantly in siTERT group, when compared with the NC and control groups. The cell cycle was accelerated in the rTERT group, and blocked in the G1/S transition in the siTERT group. The mRNA and protein levels of P27, P53 and phosphatase and tensin homolog (PTEN) decreased significantly in the rTERP group and increased in the siTERP group, while cyclin dependent kinase 2 and Cyclin D1 increased significantly in the rTERP group and decreased in the siTERP group. The expression of cell division cycle 25A did not alter significantly. The protein levels of β‑catenin and retinoblastoma were also unaltered. Protein kinase B (AKT) was detected once activated by TERT, and there were increased phosphorylated (p)‑AKT protein levels in the rTERT group, and decreased p‑AKT protein levels in the siTERT group. In conclusion, TERT could induce thyroid carcinoma cell proliferation mainly through the PTEN/AKT signaling pathway.

Proteomic analysis of selective cytotoxic anticancer properties of flavonoids isolated from Citrus platymamma on A549 human lung cancer cells

Citrus platymamma Hort. ex Tanaka (Byungkyul in Korean) has been used in Korean folk medicine for the treatment of inflammatory disorders and cancer. However, the molecular mechanism underlying the anticancer properties of flavonoids isolated from C. platymamma (FCP) remains to be elucidated. Therefore, the present study attempted to identify the key proteins, which may be important in the anticancer effects of FCP on A549 cells using a proteomic approach. FCP showed a potent cytotoxic effect on the A549 human lung cancer cells, however, it had no effect on WI‑38 human fetal lung fibroblasts at the same concentrations. Furthermore, 15 differentially expressed protein spots (spot intensities ≥2‑fold change; P<0.05) were obtained from comparative proteome analysis of two‑dimensional gel electrophoresis maps of the control (untreated) and FCP‑treated A549 cells. Finally, eight differentially expressed proteins, one of which was upregulated and seven of which were downregulated, were successfully identified using matrix‑assisted laser desorption/ionization time‑of‑flight/time‑of‑flight tandem mass spectrometry and peptide mass fingerprinting analysis. Specifically, proteins involved in signal transduction were significantly downregulated, including annexin A1 (ANXA1) and ANXA4, whereas 14‑3‑3ε was upregulated. Cytoskeletal proteins, including cofilin‑1 (CFL1), cytokeratin 8 (KRT8) and KRT79, and molecular chaperones/heat shock proteins, including endoplasmin, were downregulated. Proteins involved in protein metabolism, namely elongation factor Ts were also downregulated. Consistent with results of the proteome analysis, the immunoblotting results showed that 14‑3‑3ε was upregulated, whereas CFL1, ANXA4 and KRT8 were downregulated in the FCP‑treated A549 cells. The majority of the proteins were involved in tumor growth, cell cycle, apoptosis, migration and signal transduction. These findings provide novel insights into the molecular mechanisms underlying FCP-induced anticancer effects on A549 cells.

Up-regulation of Hsp27 by ERα/Sp1 facilitates proliferation and confers resistance to apoptosis in human papillary thyroid cancer cells

17β-estradiol (E2) has been suggested to play a role in the development and progression of papillary thyroid cancer. Heat shock protein 27 (Hsp27) is a member of the Hsp family that is responsible for cell survival under stressful conditions. Previous studies have shown that the 5'-promoter region of Hsp27 gene contains a specificity protein-1 (Spl) and estrogen response element half-site (ERE-half), which contributes to Hsp27 induction by E2 in breast cancer cells. However, it is unclear whether Hsp27 can be up-regulated by E2 and which estrogen receptor (ER) isoform and tethered transcription factor are involved in this regulation in papillary thyroid cancer cells. In the present study, we demonstrated that Hsp27 can be effectively up-regulated by E2 at mRNA and protein levels in human K1 and BCPAP papillary thyroid cancer cells which have more than two times higher level of ERα than that of ERβ. The up-regulation of Hsp27 by E2 is mediated by ERα/Sp1 and ERβ has repressive effect on this ERα/Sp1-mediated up-regulation of Hsp27. Moreover, we showed that the up-regulation of Hsp27 by ERα/Sp1 facilitates proliferation and confers resistance to apoptosis through interaction with procaspase-3. Targeting this pathway may be a potential strategy for therapy of papillary thyroid cancer.

Proteomic characterization of peroxisome proliferator-activated receptor-γ (PPARγ) overexpressing or silenced colorectal cancer cells unveils a novel protein network associated with an aggressive phenotype

Peroxisome proliferator-activated receptor-γ (PPARγ) is a transcription factor of the nuclear hormone receptor superfamily implicated in a wide range of processes, including tumorigenesis. Its role in colorectal cancer (CRC) is still debated; most reports support that PPARγ reduced expression is associated with poor prognosis. We employed 2-Dimensional Differential InGel Electrophoresis (2-D DIGE) followed by Liquid Chromatography (LC)-tandem Mass Spectrometry (MS/MS) to identify differentially expressed proteins and the molecular pathways underlying PPARγ expression in CRC progression. We identified several differentially expressed proteins in HT29 and HCT116 CRC cells and derived clones either silenced or overexpressing PPARγ, respectively. In Ingenuity Pathway Analysis (IPA) they showed reciprocal relation with PPARγ and a strong relationship with networks linked to cell death, growth and survival. Interestingly, five of the identified proteins, ezrin (EZR), isoform C of prelamin-A/C (LMNA), alpha-enolase (ENOA), prohibitin (PHB) and RuvB-like 2 (RUVBL2) were shared by the two cell models with opposite expression levels, suggesting a possible regulation by PPARγ. mRNA and western blot analysis were undertaken to obtain a technical validation and confirm the expression trend observed by 2-D DIGE data. We associated EZR upregulation with increased cell surface localization in PPARγ-overexpressing cells by flow cytometry and immunofluorescence staining. We also correlated EZR and PPARγ expression in our series of CRC specimens and the expression profiling of all five proteins levels in the publicly available colon cancer genomic data from Oncomine and Cancer Genome Atlas (TCGA) colon adenocarcinoma (COAD) datasets. In summary, we identified a panel of proteins correlated with PPARγ expression that could be associated with CRC unveiling new pathways to be investigated for the selection of novel potential prognostic/predictive biomarkers and/or therapeutic targets.

The thyroid cancer PAX8-PPARG fusion protein activates Wnt/TCF-responsive cells that have a transformed phenotype

A chromosomal translocation results in the production of a paired box 8-peroxisome proliferator-activated receptor gamma (PAX8-PPARG) fusion protein (PPFP) in ∼35% of follicular thyroid carcinomas. To examine the role of PPFP in thyroid oncogenesis, the fusion protein was stably expressed in the non-transformed rat thyroid cell line PCCL3. PPFP conferred on PCCL3 cells the ability to invade through Matrigel and to form colonies in anchorage-independent conditions. PPFP also increased the fraction of cells with Wnt/TCF-responsive green fluorescent protein reporter gene expression. This Wnt/TCF-activated population was enriched for colony-forming and invading cells. These actions of PPFP required a functional PPARG DNA binding domain (DBD) within PPFP and were further stimulated by PPARG agonists. These data indicate that PPFP, through its PPARG DBD, induces Wnt/TCF pathway activation in a subpopulation of cells, and these cells have properties of cellular transformation including increased invasiveness and anchorage-independent growth.

A long non-coding RNA, PTCSC3, as a tumor suppressor and a target of miRNAs in thyroid cancer cells

Papillary thyroid carcinoma susceptibility candidate 3 (PTCSC3) is a newly identified non-coding RNA, which is highly thyroid-specific. Dramatic downregulation in thyroid cancers suggests its potential roles in the occurrence and development of thyroid tumors. The present study aimed to investigate the effects of PTCSC3 on the biological features of thyroid cancer cells and to explore its possible function as a competing endogenous RNA to bind with miRNAs. Constructs containing the long non-coding RNA, PTCSC3, were transfected into various thyroid cancer cell lines (BCPAP, FTC133 and 8505C). Cell growth, cell cycle transition and apoptosis were measured by MTT assay and flow cytometry. In silico analysis was performed to identify the binding site of PTCSC3 for target miRNAs. Additionally, detection of putative miRNA by quantitative reverse transcription-polymerase chain reaction (RT-PCR) in thyroid cancer cells transfected with PTCSC3 was determined to confirm the interaction. Following transfection with PTCSC3, all three thyroid cancer cells originating from various pathological types of thyroid cancers demonstrated significant growth inhibition, cell cycle arrest and increased apoptosis. The top 20 miRNAs to have a potential interaction with PTCSC3 were identified, out of which miR-574-5p was selected to further confirm the inverse correlation with PTCSC3 in thyroid cancer cells in vitro. In the present study, PTCSC3 as a tumor suppressor was investigated as a competing endogenous RNA for miR-574-5p.